Abstract
Fibrous minerals may occur as minor impurities in metamorphic limestone, dolomite, and altered magmatic or metamorphic silicate rocks. The processing or use of the crushed products may release fibrous airborne dust. To evaluate the need for safety measures, 216 samples of rocks, products, and dusts from 9 limestone or dolomite mines and 9 rock quarries were taken. The fiber concentrations were quantified as weight-% and fiber number per mass unit by scanning electron microscopy with microanalysis. All silicate fibers at least 5 urn in length, less than 3 μm in diameter, and with an aspect ratio of at least 3:1 were classified as perfect fibers, fibrous cleavage fragments, or cleavage fragments. The electron microscopic method enabled the mineralogical identification of the particles and the determination of their morphology. The fibers were also counted according to various criteria of aspect ratios.